J. nat. Rubb. Res., 2(3), 191-199

The Biology and Ecology of nigricornis and Its Control in the Cover Plants under in Malaysia

ABU BAKAR ATIM*, SINNAH GOPALAN* AND MOHD AKIB YUSOF* Biological and ecological investigations of the pest Valanga in leguminous cover plants under rubber were studied in the laboratory and field. Field studies were carried out by sampling the natural population of Valanga as well as its natural enemy, Tenodera aridifolia. Laboratory studies were based on field observations of the seasonal abundance of adults and nymphs predator-prey relationships to size and susceptibility ofnymphal instar and field application rates of selected insecticides in wooden cages, Pueraria phaseoloides was found to be not only an ideal trap-crop for the development of beneficial , but also Valanga. For the long-term control of Valanga, efforts should be made in controlling the nymphs before they became adults. Scouting for the presence of nymphs should be made as early as August, In the event of a population outbreak, chemical control should be exercised to kill adults as well as nymphs. For quick killing of Valanga nymphs which were less mobile, insecticides in descending order of effectiveness were acephate (Orthene 75 S), chlorpyritos (Lorsban 40 EC), methamidophos (Tamaron 50 EC) and dieldrin (Dieldrex 15).

Entomophagous insects play an important role insecticides have been in use for a long time in regulating the population of pest producing undesirable residues on cover plants species and are an important component in pest and inducing resistance in pests. Therefore, management systems. Knowledge of predator there is an urgent need for safe and effective and prey relationships is vital for the develop- insecticides for use on cover plants. ment of programmes for conservation or augmentation of the insects in an agricultural The cultural practice of planting cover plants ecosystem. The future use of chemical control within rubber attracts insects especially Valanga should not only rely on safer chemicals, but and its natural enemies such as Tenodera should also be based on the biology and ecology aridifolia (mantis). Controlling the actively of the pest and its natural enemies. mobile Valanga adults has been difficult. Normally the covers are severely damaged () is a well- before any control measures can be exercised known pest of cover plants and young rubber (Figure 1). in commercial plantations1'2. At present there are no satisfactory methods of control for field This investigation reports on the seasonal including Valanga3'6 other than abundance of Valanga, the predator-prey insecticides. Although dieldrin and malathion relationships within the cover plants and the have been recommended for grasshopper effective biological and chemical control of control, they have not been effective. These Valanga on a long-term basis.

"Rubber Research Institute of Malaysia, P.O. Box 10150, 50908 Kuala Lumpur, Malaysia

191 Journal of Natural Rubber Research, Volume 2, Number 3, September 1987

Figure 1. Damage caused by Valanga nigricornis on Pueraria and on rubber seedling.

MATERIALS AND METHODS were not counted but their abundance with Valanga and Tenodera in the samples were Population Trends of Valanga and Tenodera recorded. Records of field temperature and in Leguminous Cover Plants relative humidity were obtained from a thermo- hygrograph and rainfall from a rain gauge The seasonal trends of Valanga and located near the Experiment Station. Tenodera in a leguminous cover field of Pueraria near the Rubber Research Institute Experiment Station were monitored during the Laboratory Studies on the Biology of Valanga years 1984 and 1985. Weekly, from September and Tenodera 1984 to December 1985, four samples, each Adults of Valanga were collected from the consisting of fifty sweeps were taken from each fields and reared on diets of Pueraria leaves and field using a standard sweep-net (40.6 cm in chicken feed. The adults held in 1 x 1 x 1 m3 diameter, 66.0 cm handle, and 63.5 cm deep wooden cages with fine wire netting were conical bag) swung in a 180° arc. The four sets provided with laying trays containing soil for of samples were taken at random from each oviposition. The eggs were collected and upon field by sweeping the leguminous cover plants hatching, the nymphs were held in 0.5 x 0.5 in the interrow of three-year-old rubber and the x 0.5 m3 wooden cages with wire netting and nymphs of Valanga and Tenodera were the life cycle was thus studied. counted. The adults of both insects were counted by visual observation during sweeping. Adults of Tenodera collected from Pueraria Valanga adults that flew from the interrow and covers were housed in cages similar to those of Tenodera adults, which were less mobile and Valanga. They were fed with crickets and sometimes caught in the sweep-net, were grasshopper nymphs. Upon oviposition and counted along with those observed on the hatching, the parents were transferred into the plants. Other entomophagous insects and pests wooden cages. The young mantis were reared

192 COPYRIGHT © MALAYSIAN RUBBER BOARD Abu Bakar Atim et al.: Biology and Ecology of Valanga nigricornis and Its Control on pests of leguminous cover such as smaller RESULTS nymphs of cricket and grasshoppers until adulthood. The life cycle, the generation The data showing the abundance of adults and interval of the nymphal instar and the size of nymphs of Valanga and Tenodera for 1984 and the predator (Tenodera) and prey (Valanga) 1985 are shown in Figure 2. Field and during the developmental period were studied. laboratory studies of Valanga showed that adults started laying eggs in the soil during Predator-prey Relationships between Valanga August. These eggs remained dormant for more and Tenodera than two months, then hatched at the onset of the rainy season. Nymphal population began Nymphal populations of Valanga and to build up in high numbers through June and Tenodera were cultured in large numbers in the once adulthood was reached they were laboratory. Due to the abundance of nymphal long-lived. populations of another grasshopper, Steno- In Pueraria three peaks of population occurred catantops sp. with Valanga during sampling, around September 1984, April 1985 and the former nymphs were also reared in large September 1985. The population of adults in numbers in the laboratory for the feeding trials. April 1985 was as high as in September 1985. Selected life stages of the third, the sixth and However oviposition in the soil occurred only the adult stage of praying mantis were given the around September in that year. In April, most choice of feeding on Valanga or Stenocatantops of the egg cases were found openly laid on cover nymphs of the second and the fourth instar plants instead of the soil. This coincided with respectively. Each selected life stage of the the wet season experienced at the Station. praying manis was offered twenty prey of each species (preliminary test indicated that laying Field and laboratory studies indicated that female mantis could consume at maximum ten Tenodera lay eggs upon reaching adulthood. second instar Valanga per day). The number Nymphal population was generally lower in of prey was maintained to twenty daily for August, then peaked at the highest around three days. An assessment was carried out on May. By that time most Valanga had become the potential voracity of the two prey items adults. commonly found in covers. Laboratory Studies on the Biology of Valanga Laboratory Control Studies of Valanga and Tenodera The less mobile stage of the second instar The developmental period of the life stages Valanga (presumed to be vulnerable to insecti- of Valanga as well as Tenodera under varying cides) was reared in sufficient numbers by the weather conditions in the cages of an open method described earlier for studies on the glasshouse at the Experiment Station is shown toxicity of selected insecticides. The insecticides in Table 1. selected were methamidophos (Tamaron 50 EC), acephate (Orthene 75 S), chlorpyritos In general, the developmental period of the (Lorsban 40 EC) and dieldrin (Dieldrex 15). nymphal stages of Valanga was much shorter They were selected for their capability in killing than Tenodera. However, the incubation period the adults and nymphs quickly while providing of the egg stage of Valanga was twice as long long-term activity. Two methods of exposure as Tenodera. Valanga eggs took about two to insecticides were used to evaluate the potency. months to hatch. The day interval of each In the first method, Valanga nymphs were instar from the first through the seventh into immediately introduced after leguminous cover adulthood was about one week. Relative to of Pueraria was sprayed; in the second, the size, Tenodera in general is longer than Valanga nymphs were introduced 2 h after the spraying in length throughout the nymphal stages and of chemical. In both methods, assessment of through adulthood except for the first instar. the mortality of Valanga was carried out at 24 h Nymphal predation by Tenodera occurred with and 48 h after introduction. the younger stages of Valanga especially the

193 30

•———• Valanga (adults) O-——O Valanga (nymphs) 25 •———• Tenodera (adults) ——a Tenodera (nymphs)

20

O O (N

15

cO 15 10 o E-

Sep. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Oct. Nov. Dec. *—————1984 —————> <————————————————————— 1985 —————————————————————————> Figure 2. Monthly total of Valanga and Tenodera under Pueraria. Abu Bakar Atim et ai: Biology and Ecology of Valanga nigricornis and Its Control

TABLE 1. DEVELOPMENTAL LIFE STAGES OF VALANGA AND TENODERA IN THE LABORATORY

Valanga Tenodera Stage X developmental X developmental period (days) S.E. period (days) S.E.

Egg hatching 67.5 ± 1.19 23.0 ± 0.71 1st instar 10.3 ± 0.25 8.8 ± 0.25 2nd instar 8.0 ± 0.41 7.8 ± 0.25 3rd instar 8.8 ± 0.25 5.8 ± 0.25 4th instar 8.8 ± 0.25 7.0 ± 0 5th instar 9.8 ± 0.25 8.0 ± 0 6th instar 10.8 ± 0.25 7.3 ± 0.25 7th instar 10.3 ± 0.25 8.0 ± 0 Adult 10.8 ± 0.25 13.8 ± 0.25 Premating 14.8 ± 0.25 8.3 ± 0.25 Preoviposition 31.8 ± 0.25 15.5 ± 0.25 Adult longevity 84.3 ± 3.61 116.3 ± 1.75 first, second, third and fourth instar, provided There was a strong correlation between the the size of the predator was larger than the prey. population of Valanga nymphs and Tenodera Although The subsequent stages of Valanga adults in the Pueraria covers in 1985 (Figure 3). were shorter than Tenodera, observation The population of Tenodera increased over the indicated that Tenodera seldom feed on prey from May through October, then nymphal nymphs in the field. population of Valanga increased over Tenodera adults. Predator-prey Relationships between Valanga and Tenodera Laboratory Controlled Studies of Valanga When equal-sized grasshopper nymphs The analysis of variance indicated that the (second nymphal instar of Valanga and fourth toxicity of the chemical and time of application nymphal instar of Stenocatantops) were offered played a pivotal role in controlling adults and to the third instar of Tenodera, there was no nymphs of Valanga, either upon contact or significant difference in the amount of the two upon feeding on the residues left on the leaves prey consumed (Table 2). The third instar of of Pueraria covers after spraying. Chlorpyritos mantis that was larger than its prey showed (Lorsban 40 EC) and acephate (Orthene 75 S) equal preference and the consumption was were significantly better than methamidophos about seven individual prey per predator per (Tamaron 50 EC) and dieldrin (Dieldrex 15) in 72 hours. As the size of the mantis became larger killing nymphs of Valanga upon contact (sixth nymphal instar), their consumption of (Table 5). Valanga was significantly higher than their consumption of Stenocatantops (Table 3). The When residues of chemical were left on leaves average amount of Valanga and Stenocatantops 2 h after spraying, all the four chemicals tested nymphs consumed was fourteen and fifteen per were good in controlling Valanga nymphs. predator per 72 h respectively. Adult mantis However, chlorpyritos (Lorsban 40 EC) caused consumed even higher numbers of Valanga significantly higher numbers of mortality than Stenocatantops nymphs (Table 4). among Valanga nymphs than methamidophos

195 TABLE 2. CONSUMPTION BY THIRD INSTAR TENODERA OF THE VALANGA AND STENOCATANTOPS NYMPHS WITHIN 72 H

No. of prey consumed Rep. no. Valanga Stenocatantops Total Observed Expected Observed Expected

I 8 7.5 7 7.5 15 II 9 7.5 6 7.5 15 III 7 7.0 7 7.0 14 IV 8 7.5 7 7.5 15

Total 32 27 59

X2 = 0.73

TABLE 3. CONSUMPTION BY SIXTH INSTAR TENODERA OF THE VALANGA AND STENOCA TANTOPS NYMPHS WITHIN 72 H

No. of prey consumed Rep. no. Valanga Stenocatantops Total Observed Expected Observed Expected

I 13 8.0 3 8 16 II 16 12.5 9 12.5 25 III 10 6.5 3 6.5 13 IV 15 9.0 3 9.0 18

Total 54 18 72

X2 = 19.97 2 •* 0.05 = 7.82

TABLE 4. CONSUMPTION BY ADULT TENODERA OF VALANGA AND STENOCATANTOPS NYMPHS WITHIN 72 H

No. of prey consumed Rep. no. Valanga Stenocatantops Total Observed Expected Observed Expected

I 14 10.5 7 10.5 21 II 19 13.5 8 13.5 27 III 15 10.0 5 10.0 20 IV 16 12.0 8 12.0 24

Total 64 28 92

XL = 14.48 X*. = 7.82 Abu Bakar Atim et al.: Biology and Ecology of Valanga nigricornis and Its Control

100 r

"•'•" — Valanga nymphs (y = 2.3 + 3.13x + 2.5x2) 80 — - Tenodera adults (y = 28.0 -I- O.SOx - 0.37x2)

60

40

U 20

-20 1 1 I 1 i i 1 I 1 i i 6 — 5 -4 -3 -2 — 1 0 1 2 3 4 5 J F M A M J J A S O N D Month Figure 3. Monthly distribution o/Valanga nymphs and Tenodera adults in Pueraria.

TABLE 5. EFFECT OF INSECTICIDES ON THE MORTALITY OF VALANGA NYMPHS INTRODUCED IMMEDIATELY AFTER SPRAYING OF PUERARIA COVER LEAVES

Dead Valanga after treatment (%) Treatment Concentration 24 h 48 h Mean3

Control (water) 0 0 0 0 Methamidophos (Tamaron 50 EC) 5 ml/9 litres 50.0 80.0 65.0 Acephate (Orthene 75 S) 5 g/9 litres 75.0 100.0 95.0 Chlorpyritos (Lorsban 40 EC) 1:100 90.0 100.0 87.5 Dieldrin (Dieldrex 15) 1:400 45.0 100.0 72.5

Mean 65.0 95.0 80.0

*Mean and ANOVA do not include control. L.S.D.,)^ Time = 13.33

L.S.D.OOS Insecticide = 18.85

(Tamaron 50 EC), acephate (Orthene 75 S) and DISCUSSION dieldrin (Dieldrex 15) upon contact as well as It was observed during field scouting that the ingestion (Table 6). younger stages of Valanga, especially the first

197 Journal of Natural Rubber Research, Volume 2, Number 3, September 1987

TABLE 6. EFFECT OF INSECTICIDES ON THE MORTALITY OF VALANGA NYMPHS INTRODUCED IMMEDIATELY 2 H AFTER SPRAYING OF PUERARIA COVER LEAVES

Treatment Concentration Dead Valanga after treatment (%) 24 h 48 h Mean3

Control (water) 0 0 0 0 Methamidophos (Taraaron 50 EC) 5 ml/9 litres 55.0 90.0 72.5 Acephate (Orthene 75 S) 5 g/9 litres 55.0 95.0 75.0 Chlorpyritos (Lorsban 40 EC) 1:100 90.0 100.0 95.0 Diddrin (Dieldrex 15) 1:400 50.0 95.0 73.0

Mean 53.3 93.0 73.0

aMean and ANOVA do not include control and chlorpyritos (Lorsban 40 EC).

L.S.D.005 Time = 16.61

L.S.D.005 Insecticide = 20.34 and second instar, were consumed by assassin suffocation or immobility of nymphs and thus bugs, spiders, tiger beatles and robber flies as increased changes of predation by biological well as by Tenodera. Leguminous cover plant agents. Indirectly, rainfall probably affected such as Pueraria is an ideal trap-crop for the the ovipositional behaviour. It may be that the development of beneficial insects, but such drier condition of the soil was ideal for ovi- cover plants also attract Valanga. Since the position and eggs laid in the soil were protected nymphal stages of Valanga are less mobile and from their natural enemies, thus producing most vulnerable to insecticides, any control higher survival rates. For the long-term control measures should be directed at the nymphs. The of Valanga one should take into account the adults are highly dispersed, long-lived and pests, preference for the particular crop, the difficult to control. time of application, the vulnerable stages of the insect, the natural enemies present and the Field scouting for nymphs of Valanga should biology of the pest and its natural enemies. commence in August. In the event of a popula- tion outbreak, either chlorpyritos (Lorsban ACKNOWLEDGEMENT 40 EC) or acephate (Orthene 75 S) can be used effectively to kill adults and nymphs. The The authors wish to express their deep ap- application of insecticides should be targeted preciation to Dr Tan Ah Moy and Dr C.K. at the nymphs that are normally found from John for their support and advice in the September through June. With respect to control preparation of this paper. Thanks are also due of leguminous cover plants such as Pueraria to Encik Abdul Malik Yaakob and Encik which are tolerant to damage, spraying can be Mohamad Haji Baharin for the support of the delayed as long as the nymphs have not reached field works. Lastly, the authors are indebted to adulthood. This is to take advantage of preda- Puan Zakiah Yatim, Puan Asmah Haji Jantan tion by the natural biological agents. The study and Puan Jeyanayagi Indran for the typing of revealed that as the population of Valanga the manuscript and drawing of the figures nymphs increased from around October through respectively. March, Tenodera started feeding on the two species of grasshopper nymphs. Rainfall had REFERENCES a detrimental effect on the survival rate of 1. RAO, B.S. (1965) Pests of Hevea Plantations in Valanga nymphs either directly or indirectly. Malaya. Kuala Lumpur: Rubber Research Institute The immediate effect of rainfall could either be of Malaysia.

198 Abu Bakar Atim et al.: Biology and Ecology of Valanga nigricornis and Its Control

2. RAO, B.S. (1964) Pests of Leguminous Covers sanguinipes and Camnula pelluside (: in Malaya and Their Control. Planter, Kuala ). Can. Entomol, 107, 543. Lumpur, 40, 274. 5. ONSAGER, J.A. (1978) Efficacy of Carbaryl Applied 3. HEWITT, G.B. AND ONSAGER, J.A. (1980) A to Different Life Stages of Rangeland Grass- Comparison of Two Methods for Estimating Forage hoppers. /. Econ. Entomol, 71, 269. Destruction by Grasshoppers. J. Econ. Entomol., 73, 657. 6. SKOOG, F.E., COWAN, F.T. AND CONNIN, R.V. 4. MCKINLAY, K.S. AND BURRAGE, R.H. (1975) (1961) Laboratory and Field Tests of New Insecti- Laboratory and Field Experiments on the Toxicity cides for Grasshopper Control. J. Econ. Entomot, of Various Insecticides to Grasshoppers, Melanoplus 54, 170.

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